It is an object of the present invention to improve the running performance on snowy and icy roads, and for this purpose, blocks provided with sipes are formed at a tread portion. The sipes include an open top end that opens at a block surface and a bottom, and a configuration of the sipes in a plane parallel with the block surface comprises a zigzag part extending in the length direction of the sipes. The zigzag part displaces upon turning back to one side and to the other side in a length direction of the sipes in the course from the open top end to the bottom. At least one block includes a first sipe and a second sipe which depths of the turn-back points of displacement from the open top end and/or positions of the turn-back points of displacement in the length direction differ from each other.